dual flush valve

ABSTRACT

A dual flush valve ( 1 ) comprises a housing ( 10 ) having an outlet ( 2, 36 ) and a main valve assembly ( 34 ) movable within the housing between a raised position in which the valve is open and a lowered position in which the valve is closed. An operating system ( 14 ) is actable in response to an input to raise the main valve assembly ( 34 ) off its seat ( 2 A) so that it is subjected to an upwards force by immersion fluid entering the outlet. In response to a first actuation input, the operating system exerts a first downward force on the main valve assembly ( 34 ) so that the main valve assembly is caused to descend when the fluid in the cistern reaches a first predetermined intermediate fluid level ( 31 ) to provide a partial flush. In response to a second actuation input the operating system exerts a second downward force on the main valve assembly ( 34 ) which is lower than the first downward force so that main valve assembly is caused to descend when the fluid in the cistern reaches a second predetermined intermediate fluid level ( 32 ) lower than the first intermediate fluid level to provide a full flush.

This invention relates to a dual flush valve for emptying or partly emptying cisterns and is particularly, although not exclusively applicable to being used for flushing domestic toilets.

In order to meet ever increasingly stringent water saving and environmental requirements, dual flush valves have become a main established means for flushing domestic toilets and to enable compliance with regulation requirements for reducing the amount of water used for flushing, almost invariably dual flush valves tend to be fitted in tall slender (portrait) cisterns. However, notwithstanding that generally most valves achieve an adequate performance, there are valves, which for any of a number of reasons have only a marginal performance with the consequence that in some cases it can on occasions be necessary to operate the full flush control more than once to effectively clear the toilet pan; the most likely causes for this being due to any of the following reasons: the valve being incompatible with the particular combination of cistern and pan, incorrect setting or limited adjustment of the valve not permitting the cistern water filling level to be set sufficiently high or the valve's partial flush level being fixed and at a too low a level—particularly in a landscape cistern.

To overcome these and similar or related problems, the present invention proposes a dual flush valve for enabling high or optimum performance to be achieved for almost any cistern or W.C. in which it is incorporated: providing easy independent setting of partial and full flush levels/volumes for meeting both national and international regulation requirements, with in addition there being provision for operation with cisterns filled to, or approaching maximum permitted filling levels. Moreover with this flexibility, the invention is well placed to meet any future requirements for further reductions in flushing volumes and achievement of related water saving initiatives.

This invention is a development of my previous invention, Dual Discharge Valve, European Patent No. EP1297226B1, International Application No. PCT/GB2001/002767 (International publication number WO2002/001010.

According to the present invention there is provided a dual flush valve for immersion in a fluid in a cistern, the valve comprising: a main valve assembly, an outlet having a valve seat for the main valve assembly, a guide structure for positioning and guiding the main valve assembly relative to the outlet for movement between a lowered position in which the main valve assembly locates on the valve seat to seal the outlet to prevent immersion fluid flowing from the cistern through the outlet and a raised position in which the outlet is not sealed; an operating system actuable in response to an input to raise the main valve assembly off its seat so that on raising the main valve assembly the main valve assembly is subjected to an upwards force by immersion fluid entering the outlet, thereby causing it to rise to permit full flow of immersion fluid through the outlet, the operating system having a mechanism for subsequently exerting a downward force on the main valve assembly sufficient to exceed any buoyancy force and fluid level dependent flow reaction and pressure forces acting upwards on the main valve assembly so that the main valve assembly descends and reverts to its lowered seated position when the fluid in the cistern reaches a pre-determined level; characterised in that the operating system is operative in response to a first actuation input to exert a first downward force on the main valve assembly so that the main valve assembly is caused to descend and revert to its lowered, seated position when the fluid in the cistern reaches a first predetermined intermediate fluid level and is operative in response to a second actuation input to exert a second downward force on the main valve assembly which is lower than the first downward force so that the main valve assembly is caused to descend and revert to its lowered, seated position when the fluid in the cistern reaches a second predetermined intermediate fluid level lower than the first intermediate fluid level.

Thus the downward forces exerted on the main valve assembly by the operating system will be sufficient to exceed any buoyancy forces and water level dependent flow reaction and pressure forces acting upwards on the surfaces underneath the main valve assembly in order to achieve the desired respective re-seating for a partial or full flush. Unlike the prior art, the ability to provide two different and preferably independently adjustable downward forces for defining the partial and full flush modes, the full flush level need not result in a complete or substantially complete emptying of the cistern but can be set at an intermediate level between the partial flush and empty.

Typically in the form of a short tail-pipe the surface below the valve seat is preferably frusto-conical tapering towards the outlet and is also preferably of concave configuration.

The guide structure may be a housing within which the main valve assembly is movable between lowered and raised positions, the housing having a lower housing portion in which the valve seat is provided, a wall of the lower housing portion having openings through which immersion fluid can flow to the outlet when the main valve assembly is raised off the valve seat.

In one embodiment, the housing has an upper portion separated from the lower portion by a partition plate to define upper and lower chambers, the valve including a first vent means through which fluid may pass between the upper and lower chambers, a second vent means within the upper chamber between the main valve assembly and a wall of the upper housing portion through which fluid may flow from one end of the upper chamber to the other, a third vent means towards the upper end of the upper housing portion through which immersion fluid can flow between the upper chamber and the surrounding cistern, the main valve assembly including a central stem which projects upwardly beyond the upper end of the housing for co-operation with the operating system.

The central upwardly extending stem is preferably a hollow stem protruding above the normal full level setting of the water in the cistern and so provides a convenient and efficient discharge route to the outlet in the event of water rising above the normal full level setting. The invention is more specifically described below with reference to a hollow stem, although it will be appreciated that this is not essential.

The first vent means may be a restrictive passage or one or more non restrictive flow apertures between the upper and lower chambers—with generally the restricted passage only being necessary for any applications where the cistern is emptied, to restrict the flow from the upper chamber to the lower chamber during the final stages of emptying.

For enabling the displacement and transfer of water from end to end of the upper chamber as the main valve assembly rises or descends within it, a second vent means is provided, which conveniently may be an annular gap between the main valve assembly and the upper housing wall. However in applications where the valve first vent means is non-restricted, the requirement and function of the second vent means may be significantly reduced, since water ejected from the top of the upper chamber through the third vent means by the rising main valve assembly is balanced by water readily flowing from the lower chamber into the bottom of the upper housing via the first vent means.

The third vent means may be one or more large apertures as this accommodates either a restricted or a non-restricted first vent means—with in the case of the restricted first vent means, the third vent means mainly providing a free communication at the top of the upper chamber with the surrounding cistern; whereas in the case of the non-restricted first vent means, the third vent means provides for ejection and replenishment of water in the upper chamber, displaced by the main valve assembly.

On cessation of flow into the outlet following either a full flush or a partial flush operation, if the water level in the cistern has fallen below the top of the upper housing/third vent means, air will enter the upper chamber through the third vent means which results in water flowing from the upper chamber via the second and first vent means, with this continuing until the water level in the upper chamber reaches the same level as that in the surrounding cistern. Similarly where the full flush empties the cistern, air enters the upper chamber via the third vent means as a result of the water level in the cistern falling below the top of the upper housing. With the main valve initially remaining in the raised position, water flows from the upper chamber via the second and first vent means until the water level in the upper chamber has fallen to a point where the buoyancy of the main valve assembly and flow reaction and pressure forces are no longer sufficient to support the weight of the main valve and hollow stem assembly (since when emptying the cistern, no downward force is applied by the second or full flush operating means). Moreover from this point on, the rate of descent of the main valve and hollow stem assembly to the re-seated position is mainly controlled by the flow from the bottom of the upper chamber via the (restricted passage) first vent means.

With the valve re-seated following a full flush emptying of the cistern, as refilling takes place water enters the upper chamber via the restricted passage; with as the water level rises in the upper chamber, the displaced air passing through the gap between the inside wall of the upper housing and the outside of the main valve assembly and is ejected through the apertures at the top of the upper housing. Refilling continues in this manner until the water level in the surrounding cistern has risen to the top of the upper housing, at which point, water from the cistern will flow through the apertures in the top of the upper housing into the upper chamber to totally fill it, should the water level in the upper chamber be less than the level of water in the cistern.

Similarly, with the valve re-seated following either a full flush or partial flush to an intermediate water level below the apertures in the top of the upper housing as refilling takes place, water will initially enter the upper chamber via the restricted or non-restricted passage(s) at the bottom of the upper chamber to replenish any fall in fluid level in the upper chamber—this then being followed by, when the water level in the cistern reaches the top apertures, water from the cistern flowing into the top of the upper chamber to make up any difference in level.

With the valve re-seated except for the early stages of refilling from empty, where the seating force is mainly due to the weight of the main valve and hollow stem assembly, throughout refilling up to and including the final filled level the seating force is provided both by the weight of the assembly and the net hydrostatic force acting down on the main valve assembly and hollow stem assembly.

For the majority of applications, where it is not required that the cistern is emptied on the full flush, the first, second and third vent means can be dispensed with and thus the upper housing chamber and partition plate is also not required and can be replaced by a simpler housing or other structure for guiding and locating the main valve assembly relative to the seat.

The downward forces exerted separately by the first and second operating means may be applied by direct means, e.g. a catch mechanism or a latching device engaging with a detent, e.g. a flange or similar feature on the main valve assembly to apply the selected downward force to the raised main valve assembly via a spring or other force producing means—the force disengaging on or before re-seating of the valve assembly.

Actuation of the first and second operating means may be via a single cable or similar type of control with two distinct positions and preferably have a single downward force producing means. The operating system may include first and second mechanisms for applying downward forces to the main valve assembly, movement of the operating system to a first position in response to the first actuation input causing the first mechanism for applying the first downward force to engage with the main valve assembly, whilst moving the operating system to a second position in response to the second actuation input causes the first mechanism to be disengaged or not to be selected and results in engagement of the second mechanism with the main valve assembly for applying the second downward force.

Other than for bespoke cistern installations, it is preferred that the force producing means is adjustable to enable the first and second flush levels to be set independently to suit almost any cistern and typically the first mechanism, when operated will discharge water from the cistern causing the water level to fall from its set filling level to the first intermediate flush level for providing a partial flush and similarly the second mechanism, when operated will cause the water level to fall from the set filling level to the second intermediate flush level, which intentionally will be set to be substantially lower than the first intermediate level to enable a larger volume of water to be discharged from the cistern sufficient to provide a full flush. It follows that in a typical configuration, the first mechanism would be for providing the partial flush and thus the second mechanism means would be for providing the full flush. However, although in the majority of cases on completion of a full flush, the main valve assembly will re-seat leaving a substantial amount of water in the cistern above the outlet, the second mechanism may be adjusted to enable the cistern to empty, whereby on nearing completion of the full flush operation the water level would fall until it was in the vicinity of the outlet.

The operating system may comprise a sliding carrier movable from a lower, retracted position to first and second raised positions in response to the first and second actuation inputs respectively, the carrier being biased to the retracted position by a resilient member and carrying a lifting flange for contact with an abutment member on the main valve assembly to lift the main valve assembly off its seat as the carrier is moved from the retracted position to either one of the first and second raised positions.

The carrier may also comprise a catch moveable between an engagement position, in which the catch is able to contact the main valve assembly to apply a first downward force on the main valve assembly as the carrier descends towards the retracted position under the bias of the resilient member when the actuation input is removed, and at least one retracted position, in which the catch member is unable to contact the main valve assembly, the operating system including a first lug for contact with the catch to move the catch to the engagement position as the carrier moves from the retracted position to the first raised position, and a second lug for contact with the catch as the carrier approaches its retracted position from a raised position to move the catch to a retracted position.

In one embodiment, the second raised position is above the first raised position, the operating system having a third lug for contacting the catch as the carrier moves from the first raised position to the second raised position to move the catch to a retracted position.

In an alternative embodiment, the second raised position is lower than the first raised position such that during movement of the carrier to the second raised position, the first lug is not operative on the catch which remains in a retracted position.

The sliding carrier may have a further abutment for contact with the valve member to apply a downward force on the main valve assembly as the carrier descends towards the retracted position from the second raised position under the bias of the resilient member when the actuation input is removed. The operating system may be configured such that on descent of the sliding carrier from the first raised position on removal of the first actuation input, the catch engages the main valve assembly at a first intermediate position of the carrier and that on descent of the sliding carrier from the second raised position in response to removal of the second actuation input, the further abutment contacts the raised main valve assembly at second intermediate position of the carrier which is lower than the first intermediate position. Where the main valve assembly has a central stem, the central stem may carry an abutment for contact with the catch when in the engaged position and the further abutment on the sliding carrier. The further abutment may be an adjustment screw and the resilient member may be a compression spring.

For a better understanding of the invention, the main embodiments will be described by way of example only, with reference to the accompanying drawings, wherein:

FIG. 1 shows a part sectional arrangement of a dual flush valve with a two position operating system for actuation of partial and full flush operation, the valve being in the closed position;

FIG. 2 shows a view on arrow ‘A’ of FIG. 1, depicting the operating system of FIG. 1;

FIG. 3 shows the relative system/catch positions for the operating system of FIG. 1, on opening the valve for partial flush operation;

FIG. 4 shows the relative system/catch positions for the operating system of FIG. 1, on opening the valve for full flush operation;

FIG. 5 shows the relative system/catch positions with an alternative catch arrangement for the operating system of FIG. 1, on opening the valve for partial flush operation; and

FIG. 6 shows the relative system/catch positions with an alternative catch arrangement for the operating system of FIG. 1, on opening the valve for full flush operation.

FIGS. 1 and 2 show a cistern outlet/dual flush valve generally as indicated at 1, sealed and retained by a seal 3 and nut 4 into an outlet at the bottom of a cistern 15. The valve is immersed in water to a set filling level 27 and the valve is closed with a main seal 5 sealing onto outlet base 2 against seat 2A in a lower part of the valve housing to prevent the ingress of water from the cistern. The valve housing 10 has an upper chamber 13 which is filled with water and is in free communication with the water in the cistern via aperture(s) 11 and to a lesser extent by annular passage/gap 9 and restrictive passage 8. In the closed position the main valve assembly 34, which comprises float and lower hollow stem assembly 6 and upper hollow stem assembly 12, is kept in place mainly by the weight of the assembly and the marginal net downward force due to hydrostatic pressure on top of seal 5.

Inside the lower part of the valve housing, communication between the cistern water and water in the lower annular region 35A is provided by apertures 35B in the lower housing wall 35 above the seat 2A. As seal 5 is lifted off seat 2A, water from the cistern can then flow through to the outlet 2, 36.

Between the upper and lower housing is a partition plate 7 forming the top of the lower chamber and the bottom of the upper chamber. The upper chamber 13 is defined between the interior of housing wall 10A, hollow central boss 37 at the top of the upper housing and the partition plate 7, with hollow boss 40 at the bottom of the housing. The main valve assembly 34 moves up and down inside the upper chamber and generally for the arrangement shown, water is displaced from the top of the chamber to the bottom of the chamber via annular gap/passage 9 for the main valve assembly moving upwards and displaced from bottom to top for the main valve assembly moving downwards.

With the cistern filled to the set level 27, basic operation of the valve is achieved initially by lifting the main valve assembly 34 off its seat 5, 2A. This is carried out by the lifting flange 16B of sliding carrier 16 (forming part of an operating system 14), engaging with stem tang 12A and raising the said assembly above the valve seat so that water enters and fills the entrance to the outlet 36 and the said assembly rises to the fully open position. The opening sequence is initiated by operating the controls, which typically are push buttons situated on the cistern cover and connected to the operating system 14 via control cable assembly 23 and lift lever 25 to raise the sliding carrier 16 to either of two positions, each of which results in a unique action and orientation of the mechanism—one providing the partial flush, the other the full flush. The use of such dual flush controls is well known in the art and essentially comprises a two button actuation system in which depressing one button moves the cable a first distance to provide a first actuation input and depressing the other button moves the cable by a second distance to provide a second actuation input. However other operating arrangements can be used to provide two distinct actuation inputs. The cable 23 is connected with a lifting lever 25 which amplifies the movement of the cable to lift the sliding carrier 16. However, for simplification of the mechanism, lift lever 25 may be eliminated and replaced by a stroke increasing feature being incorporated in the push button unit so that control cable 23A could be directly connected to the sliding carrier.

The means of applying the required downward force to the main valve assembly is achieved by the operating system 14 which includes a spring catch mechanism, whereby independently and in conjunction with each other, the partial and full flush proportions can be conveniently varied by adjustment screws or other means at the top of the valve.

With the valve in the closed position, the sliding carrier 16 is held in the retracted position against mechanism mounting frame 18 by compression/control spring 17, the force being applied indirectly by shoulder 19A of adjustment screw/slide bar 19, through sliding carrier 16 to boss face 18A and also catch 21 is held in the retracted position by catch bosses 21A and 21C and frame lugs 18B and 18E.

FIG. 3 shows the relative catch positions in relation to FIG. 1 for partial flush operation, which commences with sliding carrier assembly 14A, comprising sliding carrier 16, catch 21, pivot 20, outrigger arm 16C and adjustment screw 22 being raised by operation of the control cable and lift lever 25 applying upward movement to sliding carrier lug 16A. The flange 16B engages with the stem tang 12A to lift the main valve assembly off its seat 5, 2A and raise it so that it rises to the fully open position, at the top of the upper housing 10.

In raising the sliding carrier assembly and main valve and hollow stem assembly to the open position, catch boss 21A comes into contact with frame lug 18C, which causes rotation of the catch about pivot 20 and for it to take up the engagement position 21(D). On release of the operating control/action, the force from the compressed control spring 17 causes the sliding carrier assembly to descend to take up the clearance between the raised stem tang position 12(B) and catch tip 21B in the extended and raised position 21(D); the catch on engaging with the stem tang being constrained by catch stop 21F (shown in FIG. 1), holding the catch in the fully extended position against the sliding carrier and lowered to the position 21(E). The spring force is thus transmitted by the catch tip 21B to the top of the raised stem tang 12A, 12(B). Also in this position with the catch engaged, outrigger arm 16C takes up the position 16(D) as indicated.

With the valve opened and the partial flush cycle initiated, the sliding carrier assembly remains in the raised position until the water level has fallen and is approaching the partial flush level 31, whereupon the upward forces on the main valve assembly are no longer sufficient to keep the valve open against the downward force applied by the sliding carrier assembly. At this point the force, mainly from the control spring causes the sliding carrier assembly to descend, carrying the main valve and hollow stem assembly with it and with additional force applied by the seal 5 intersecting the flow into the outlet the valve rapidly re-seats. On the sliding carrier assembly approaching the fully descended/retracted position, catch boss 21A contacts frame lug 18E causing the tilted catch 21(E) to disengage from the top of the stem tang 12A and return to the retracted position 21, with also boss 21C against frame lug 18B.

With the valve having just re-seated following a partial flush, the cistern refills to its normal set filling level 27—this being the point at which a conventional control float (not shown) shuts off the water inlet to the cistern.

FIG. 4 shows the relative catch positions in relation to FIG. 1 for full flush operation, which generally consist s of a partial discharge to a second and lower intermediate water level in the cistern; again commencing with the sliding carrier assembly being raised by operating the control cable to cause lift lever 25 to apply upward movement to sliding carrier lug 16A. Accordingly flange 16B engages with stem tang 12A to lift the main valve and hollow stem assembly off its seat 5, 2A and raise it so that it rises to the fully open position at the top of upper housing 10.

Again in raising the sliding carrier and main valve to the open position, catch boss 21A comes into contact with the underside of frame lug 18C, which causes initial rotation of the catch about pivot 20 from retracted position 21 to tilted position 21(D) as in FIG. 3, at which point boss 21A is clear of lug 18C. The sliding carrier with the catch in the tilted position 21(D) is raised still further and catch boss 21C comes into contact with frame lug 18D, causing the catch at the fully raised or second position of the sliding carrier, to rotate in the opposite direction to an initial retracted position 21(F). On release of the operating action, the force from the further compressed control spring causes the sliding carrier to descend until the tip 22A of full flush adjustment screw 22 on outrigger arm 16C comes into contact with the top of the stem tang in the raised position 12(B), at which point the outrigger arm takes up a position 16(E). With the sliding carrier having descended and being held at a lower position than for a partial flush, a correspondingly lower spring force is therefore applied by adjustment screw tip 22A to the top of raised stem tang 12A, 12(B). Also with the sliding carrier in this lower position, dependent on the full flush setting, the underside of catch boss 21A may have come into contact with the top of frame lug 18C and continue retraction of the catch or the catch may even be further rotated to the fully retracted and clear position 21(G).

With the valve open and the full flush cycle initiated, the sliding carrier assembly remains in the semi-raised position until the water level has fallen and in the vicinity of the full flush/intermediate level 32, whereupon the upward forces acting on the main valve assembly are no longer sufficient to keep the valve open against the downward force applied by the sliding carrier and thus the force, which is mainly, from the control spring causes the sliding carrier assembly to descend, carrying the main valve assembly with it and again with additional force applied by seal 5 intersecting the flow into the outlet, the valve rapidly re-seats. On the sliding carrier approaching the fully descended position, catch boss 21C comes into contact with frame lug 18B, which causes the catch to rotate from its fully retracted to clear position 21(G), to the normal retracted position 21, with bosses 21C and 21A in contact with or adjacent to frame lugs 18B and 18E respectively.

With the valve re-seated, refilling commences; this being virtually the same as refilling following a partial flush, except that refilling is from a lower intermediate level 32 up to the cistern set water level 27.

In the event of the inlet valve not shutting off when the cistern has filled to the set water level, the water level will continue to rise until it reaches the top edge 30 of hollow stem 12 and from then on downwards through the hollow stem and into the toilet pan.

FIG. 5 shows the relative catch positions of an alternative catch arrangement in relation to FIG. 1 for partial flush operation, which commences with the sliding carrier assembly, comprising sliding carrier 16, catch 38, pivot 20, outrigger arm 16C and adjustment screw 22 being raised by the control cable and lift lever 25, applying upward movement to sliding carrier lug 16A. This causes flange 16B to engage with the underside of stem tang 12A to lift the main valve assembly off its seat and raise it so that it rises to the fully open position.

In raising the sliding carrier and main valve assembly to the open position, catch boss 38A comes into contact with mechanism mounting frame lug 39B, which causes the catch to be rotated about pivot 20 from its retracted position 38 to the tilted or engagement position 38(C); this also being the fully raised position and higher of the two raised sliding carrier positions. On release of the operating action (e.g. push button), the force from the compressed control spring causes the sliding carrier assembly to descend to take up the clearance between the raised stem tang position 12(B) and the tip of the catch in the extended and fully raised position 38(C); the catch on engaging with the stem tang being constrained in the extended and lower raised position 38(D) by a stop (not shown) on the carrier. On engagement, the spring force is transmitted via catch tip 38B to the top of raised stem tang 12A, 12(B). At this same raised and engaged position of the sliding carrier assembly, the full flush outrigger arm takes up the position as indicated by 16(D).

With the valve open and the partial flush cycle initiated, the sliding carrier assembly remains in the raised position until the water level has fallen and in the vicinity of partial flush level 31, at which point the downward force, mainly from the control spring exceeds the upward forces acting on the main valve assembly causing the sliding carrier assembly to descend carrying the main valve and hollow stem assembly with it and with additional downward force applied by the valve seal intersecting with the flow into the outlet, the valve rapidly re-seats. As the sliding carrier assembly approaches the fully descended/retracted position, catch boss 38A contacts frame boss 39A causing tilted catch 38(D) to disengage from the top of the stem tang and return to its fully retracted position 38, with boss 38A against frame lug 39A; any further retraction or over travel being prevented by a stop (not shown) on the carrier.

With the valve re-seated, refilling (from the partial flush/intermediate level) proceeds in the manner already described for the previous embodiment.

FIG. 6 shows the relative catch positions of an alternative catch arrangement in relation to FIG. 1 for full flush operation, which commences with the sliding carrier assembly being raised by operating the control cable and the lift lever applying an upward movement to sliding carrier lug 16A. Flange 16B engages with stem tang 12A to lift the main valve assembly off its seat and raise it so that it rises to the fully open position.

In raising the main valve and hollow stem assembly to the open position, with the sliding carrier assembly fully raised to the lower of its two raised height positions and reaching the catch position 38(E) as indicated, catch boss 38A stops short of coming into contact with mechanism mounting frame lug 39B and thus with no rotation imparted to the catch, it remains in the fully retracted position. On releasing the operating action (e.g. release of a push button), the force from the control spring causes the sliding carrier assembly to descend from its fully raised height and catch position 38(E) until adjustment screw tip 22A on outrigger arm 16C comes into contact with the top of the raised stem tang 12(B) to transmit the downward force from the control spring to the main valve assembly, at which point the outrigger arm and catch take up the indicated relative positions 16(E) and 38(F) respectively.

With the valve open and the full flush cycle initiated, the sliding carrier assembly remains in the semi-raised position until the water level has fallen and in the vicinity of the full flush/intermediate water level 32, at which point the downward force, mainly from the control spring exceeds the upward forces acting on the main valve assembly, causing the sliding carrier assembly to descend carrying the main valve and hollow stem assembly with it and with additional downward force applied by the valve seal intersecting with the flow into the outlet, the valve rapidly re-seats.

As the sliding carrier assembly approaches the fully descended or retracted position, catch boss 38A approaches mounting frame lug 39A but as the catch has not been operated during the full flush cycle and remained in its retracted/un-tilted state 38, boss 38A only comes into contact with lug 39A when the sliding carrier assembly has fully descended.

Other embodiments and combinations of the invention can of course be configured.

For instance the actuation inputs could be provided by two separate rods or cables and an alternative to the screw adjustments for the partial and flush levels could be a ratchet or other stepped or settable feature. The stroke increasing device on the valve could be eliminated and replaced by incorporating the stroke increase in the push button unit.

Another alternative embodiment would consist of the main valve as in FIG. 1, with the sliding carrier linear mechanism replaced with a pivoted arm complete with spring, catch and other features for again providing independent and variable level settings for full and partial flush operations.

An alternative catch arrangement for simplifying and achieving the same function as the catch arrangement shown in FIGS. 3 and 4 would consist primarily of a catch with a single boss, similar to the catch and mechanism mounting frame lugs arrangement shown in FIGS. 5 and 6.

On raising the sliding carrier assembly to the lower of two positions, the catch boss would come into contact with the underside of the upper frame lug, causing the catch to rotate to its extended position and engage with the raised main valve assembly to apply the downward force for partial flush operation. On raising the sliding carrier assembly to its higher position, the catch boss would again come into contact with the underside of the mechanism mounting frame upper lug and the catch rotate to the extended position, beyond which with the catch fully extended and further upward movement, the catch boss and catch arm would be deflected against the lug to enable the boss to move upwards and over the upper lug from underneath to on top of it. From the fully raised position with the catch boss on top of the frame upper lug, on release of the lifting action, the force from the control spring would cause the sliding carrier assembly to descend, with initially the catch being rotated to its fully retracted position and the catch boss then being deflected as it moved downwards from on top of the mounting frame upper lug. The sliding carrier assembly would continue to descend until the full flush screw engaged with the raised main valve assembly.

For the majority of applications, where it is not required that the cistern is emptied on the full flush, the first, second and third vent means can be dispensed with and thus the upper housing chamber and partition plate are also not required and can be replaced by a simpler housing or other structure for guiding and locating the main valve assembly so that it can be raised off the outlet seat and re-seated by the operating system..

The foregoing embodiments are not intended to limit the scope of protection afforded by the claims, but rather to describe an example as to how the invention may be put into practice. 

1. A dual flush valve for immersion in a fluid in a cistern, the valve comprising: a main valve assembly, an outlet having a valve seat for the main valve assembly, a guide structure for positioning and guiding the main valve assembly relative to the outlet for movement between a lowered position in which the main valve assembly locates on the valve seat to seal the outlet to prevent immersion fluid flowing from the cistern through the outlet and a raised position in which the outlet is not sealed; an operating system actuable in response to an input to raise the main valve assembly off its seat so that on raising the main valve assembly the main valve assembly is subjected to an upwards force by immersion fluid entering the outlet, thereby causing it to rise to permit full flow of immersion fluid through the outlet, the operating system having a mechanism for subsequently exerting a downward force on the main valve assembly sufficient to exceed any buoyancy force and fluid level dependent flow reaction and pressure forces acting upwards on the main valve assembly so that the main valve assembly descends and reverts to its lowered seated position when the fluid in the cistern reaches a pre- determined level; characterised in that the operating system is operative in response to a first actuation input to exert a first downward force on the main valve assembly so that the main valve assembly is caused to descend and revert to its lowered, seated position when the fluid in the cistern reaches a first predetermined intermediate fluid level and is operative in response to a second actuation input to exert a second downward force on the main valve assembly which is lower than the first downward force so that the main valve assembly is caused to descend and revert to its lowered, seated position when the fluid in the cistern reaches a second predetermined intermediate fluid level lower than the first intermediate fluid level.
 2. A dual flush valve as claimed in claim 1, in which the guide structure comprises a housing within which the main valve assembly is movable between lowered and raised positions, the housing having a lower housing portion in which the valve seat is provided, a wall of the lower housing portion having openings through which immersion fluid can flow to the outlet when the main valve assembly is raised off the valve seat.
 3. A dual flush valve as claimed in claim 2, in which the a housing has an upper portion separated from the lower portion by a partition plate to define upper and lower chambers, the valve including a first vent means through which fluid may pass between the upper and lower chambers, a second vent means within the upper chamber between the main valve assembly and a wall of the upper housing portion through which fluid may flow from one end of the upper chamber to the other, a third vent means towards the upper end of the upper housing portion through which immersion fluid can flow between the upper chamber and the surrounding cistern, the main valve assembly including a central stem which projects upwardly beyond the upper end of the housing for co-operation with the operating system.
 4. A dual flush valve as claimed in claim 1, in which the first and second downward forces exerted by the operating system are applied to the main valve assembly by direct means, e.g. a catch mechanism or a latching device engaging with a detent, e.g. a flange or similar feature on the raised main valve assembly via a spring or other force producing means.
 5. A dual flush valve as claimed in claim 1, in which actuation of the operating system is via a single cable or similar type of control with two distinct positions to define the first and second actuation inputs.
 6. A dual flush valve as claimed in claim 1, in which the operating system includes first and second mechanisms for applying downward forces to the main valve assembly, movement of the operating system to a first position in response to the first actuation input causing the first mechanism for applying the first downward force to engage with the main valve assembly, whilst moving the operating system to a second position in response to the second actuation input causes the first mechanism to be disengaged or not to be selected and results in engagement of the second mechanism with the main valve assembly for applying the second downward force.
 7. A dual flush valve as claimed in claim 1, in which the mechanism for applying downward forces to the main valve assembly includes adjustment means configured to allow for independent adjustment of the first and second downward forces.
 8. A dual flush valve as claimed in claim 1, in which the operating system comprises sliding carrier movable from a lower, retracted position to first and second raised positions in response to the first and second actuation inputs respectively, the carrier being biased to the retracted position by a resilient member and carrying a lifting flange for contact with an abutment member on the main valve assembly to lift the main valve assembly off the valve seat as the carrier is moved from the retracted position to either one of the first and second raised positions.
 9. A dual flush valve as claimed in claim 8, in which the carrier also comprises a catch moveable between an engagement position, in which the catch is able to contact the main valve assembly to apply a first downward force on the main valve assembly as the carrier descends towards the retracted position under the bias of the resilient member when the actuation input is removed, and at least one retracted position, in which the catch member is unable to contact the main valve assembly, the operating system including a first lug for contact with the catch to move the catch to the engagement position as the carrier moves from the retracted position to the first raised position, and a second lug for contact with the catch as the carrier approaches its retracted position from a raised position to move the catch to a retracted position.
 10. A dual flush valve as claimed in claim 9, in which the second raised position is above the first raised position, the operating system having a third lug for contacting the catch as the carrier moves from the first raised position to the second raised position to move the catch to a retracted position.
 11. A dual flush valve as claimed in claim 9, in which the second raised position is lower than the first raised position such that during movement of the carrier to the second raised position, the first lug is not operative on the catch which remains in a retracted position.
 12. A dual flush valve as claimed in claim 10, in which the sliding carrier has a further abutment for contact with the valve member to apply a downward force on the main valve assembly as the carrier descends towards the retracted position from the second raised position under the bias of the resilient member when the actuation input is removed.
 13. A dual flush valve as claimed in claim 12, in which the operating system is configured such that on descent of the sliding carrier from the first raised position, the catch engages the main valve assembly at a first intermediate position of the carrier and that on descent of the sliding carrier from the second raised position, the further abutment contacts the raised main valve assembly at a second intermediate position of the carrier which is lower than the first intermediate position.
 14. A dual flush valve as claimed in claim 13, in which the guide structure comprises a housing within which the main valve assembly is movable between lowered and raised positions, the housing having a lower housing portion in which the valve seat is provided, a wall of the lower housing portion having openings through which immersion fluid can flow to the outlet when the main valve assembly is raised off the valve seat and the housing has an upper portion separated from the lower portion by a partition plate to define upper and lower chambers, the valve including a first vent means through which fluid may pass between the upper and lower chambers, a second vent means within the upper chamber between the main valve assembly and a wall of the upper housing portion through which fluid may flow from one end of the upper chamber to the other, a third vent means towards the upper end of the upper housing portion through which immersion fluid can flow between the upper chamber and the surrounding cistern, the main valve assembly including a central stem which projects upwardly be and the upper end of the housing for co-operation with the operating system, and wherein the central stem carries an abutment for contact with the catch when in the engaged position and the further abutment on the sliding carrier.
 15. A dual flush valve as claimed in claim 12, in which the further abutment is an adjustment screw.
 16. A dual flush valve as claimed in claim 8, in which the resilient member is a compression spring.
 17. (canceled) 